header {
  background-color: #f2f2f2;
  height: 100px;
  border: 1px solid black;
  box-sizing: border-box;
}
div:nth-child(1){
  background-color: #c23d3d;
  float:left;
  width: 30%;
  height: 300px;
  border: 1px solid black;
  box-sizing: border-box;
}
div:nth-child(2){
  background-color: #3d82c2;
  float: right;
  width: 70%;
  height: 300px;
  border: 1px solid black;
  box-sizing: border-box;
}
footer {
  background-color: #333;
  color: #fff;
  clear: both;
  height: 100px;
  border: 1px solid black;
  box-sizing: border-box;
}